What should I do about balance?

[smallpooldad]

Winter time has set in here in Hawaii.

The pool temps have dropped to 68F, from the normal 78F -82F. As the grandchildren are so busy they have no time for the pool. It is also very expensive to keep it heated at an average price of 35 cents per kilowatt, with the heat pump. In the past I kept the temperature up but now that the grandchildren are too busy it is a waste and electricity prices have moved up.

Also in the wintertime late October thru early March, the pool gets a lot of shade from the house, but being that it is a major architectural feature of the house I cannot drain and close it.

The balance to avoid iron build-up, has as its basis a pH of 7.4 and is normally kept as follows for 78F:

FC 4
TA 80
CH 370
CyA 70
Salt 3200
Borates (zero-dog)
CSI -0.38

At 68F the CSI is -0.47.

Could I up the Calcium (CA) to 460 for a CSI of -0.38 at 68F, or would this be detrimental in some way?

Thank you to those that might help.

 

[RobbieH]

You don't need to adjust your CSI. Since you have a plaster pool, your CH is just fine. If you get your CH too high, you start to run the risk of scaling. I'd say those numbers look perfect, nothing to do!

 

[chem geek]

Normally as the temperature drops the pH would be allowed to drift upward in which case the CSI would not change very much. However, since you've got the risk of iron staining (because I presume you've tested for iron in the water) you're in a bit of a pickle. You don't want to raise the TA because the pH probably tends to rise already due to the SWG so a higher TA would make that worse. If you want to compensate for the CSI, then yes, you can raise your CH level. Just note that any plaster degradation with a negative CSI is going to be slower at colder temperatures anyway so the risk is lower if you wanted to keep things as they are.

 

[smallpooldad]

RobbieH and Chem Geek,

Thank you to both of you for the very helpful information.

I will keep it at the current setting although I did let the pH go up to 7.7 for about a week, where it settled, but it started to cause iron staining, so I did lower it back down.

I am going to do an in-pool iron treatment just before Xmas as the pool will see action during the holidays, I normally do this once a year. Some of our children will return with their friends and some grandchildren will also use it, so there goes the utility bill.

Have a pleasant holidays.